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Frequency‐dependent conduction delay of motor‐evoked potentials in multiple sclerosis
Author(s) -
FeldbæK Nielsen Jørgen
Publication year - 1997
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(199710)20:10<1264::aid-mus9>3.0.co;2-a
Subject(s) - interstimulus interval , transcranial magnetic stimulation , stimulus (psychology) , stimulation , multiple sclerosis , latency (audio) , neuroscience , electrophysiology , audiology , psychology , medicine , psychiatry , electrical engineering , psychotherapist , engineering
Paired transcranial magnetic stimulation was applied in 33 multiple sclerosis (MS) patients and in 21 healthy controls. A major abnormality was found in latency of the second motor‐evoked potential in MS patients. At interstimulus intervals of 75, 100, and 150 ms the central motor conduction time (CMCT) was significantly prolonged in MS patients to 139%, 150%, and 125% of the CMCT of a single magnetic stimulation ( P = 0.02, P = 0.004, P = 0.03), respectively. Voluntary contraction of the target muscle abolished the difference in latency independent of the degree of contraction. Stimulation intensity influenced the length of the interstimulus interval during which the maximal conduction delay was obtained. In MS patients there was no correlation between prolonged CMCT to a single magnetic stimulus and the frequency‐dependent conduction delay to paired magnetic stimuli. It is hypothesized that the conduction delay of the conditioned response of paired magnetic stimuli in MS is of cortical origin and induced by abnormalities of the ascending volley to the neocortex. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 1264–1274, 1997